Derivative Instruments and Hedging Activities - Additional Information (Details)			1 Months Ended	3 Months Ended		9 Months Ended
	May 28, 2021	May 25, 2021	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) swap	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) swap	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Derivative [Line Items]
Subordinated borrowing interest rate	3.00%	3.00%
Aggregate fair value of net liability position				$ 60,500,000		$ 60,500,000
Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount				10,623,584,000		10,623,584,000		$ 9,211,043,000
Interest rate swaps
Derivative [Line Items]
Notional amount			$ 300,000,000
Accumulated net after-tax losses related to effective cash flow hedges				2,000,000		2,000,000		4,000,000
Reclassified to interest expense				1,800,000		1,800,000
Interest rate swaps | Fair value hedge | Noninterest Income
Derivative [Line Items]
Fee income related to derivative interest rate swaps executed with commercial loan customers				8,800,000	$ 19,200,000	22,600,000	$ 48,100,000
Interest rate swaps | Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount				$ 10,296,468,000		$ 10,296,468,000		$ 8,889,557,000
Number of instruments held | swap				27		27
Interest rate swaps | Derivatives not designated as hedging instruments: | Fair value hedge
Derivative [Line Items]
Notional amount				$ 10,400,000		$ 10,400,000
Number of instruments held | swap				2		2
Interest rate swaps | Derivatives not designated as hedging instruments: | Risk Participation Agreement
Derivative [Line Items]
Notional amount				$ 263,900,000		$ 263,900,000
Interest rate swaps | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Derivative [Line Items]
Subordinated debt basis points			2.187%